Good luck Richard! I hope it helps. You should be able to tell if you are good by recording for 20 minutes (I think the slow down is noticeable after 10 minutes).
On another note, they have released version 3.5.
I won’t have time to test if the issue has been solved there (I just sent an email to ATEM to see if they have fixed in that version).
If any of you figure out that version 3.5 is good to use please post in here.
cheers!